Depends on how the traffic is being transported and also depends on your device you’re using.
If the device you’re using (smartphone, tablet, laptop, etc.) was given to you by the school or you gave it to them at some point to connect you or add a program to it…you can safely assume that they can view everything on the device. Either they have remote capabilities and can fully view your screen as if it were you or they have detailed logs that provide information about each process that goes on on the device or both. These logs can be related to things you are doing as well as things the device is doing in the background without your input, such as updating apps.
If the device is one that you bought and own and no one has used it or installed anything to it or you didn’t install any such applications that were required for access, then you are likely on the safer side with a caveat…
When on a network like a WiFi hotspot, everything you are doing that goes across the network, whether it is to connect to local devices on the same network (like a printer or other computer) or it goes through the internet (like logging into Facebook in a web browser or in an app), these packets are being sent over this network and may be picked up by anyone who is also on the network, not just the owners or people who managed the WiFi network like the university’s IT department but also other students or guests who are also connected to the same network.
If you are accessing websites or sending data over the http protocol (www.google.com, for example), this is an unsecured protocol and you can guarantee that all data you type into this website can be viewed by anyone else on the same network with very minimal effort on their part.
But if you are using the https protocol (www.google.com, for example), your packets are encrypted. This doesn’t mean that they can not be viewed by anyone on the network, it just means that anyone who grabs these packets as you send stuff over to this website will need to either use the right key or find a way to break it which usually involves something sophisticated like a quantum computer, which some universities do have, but are unlikely using them for this purpose. But just saying, the capability is there.
It’s easy to see whether the website you are accessing is using http or https if in a web browser like Google Chrome, but it’s difficult if using it in an app because the app doesn’t tell you exactly which protocol it’s using. Most newer apps and websites are using https, but there are some outliers. You can find this out if you do some digging on your device through testing, but it’s time consuming.
Do keep in mind that http and https are only two protocols mentioned and there are vastly more protocols out there for other tasks such as peer to peer networking like in torrents, FTP and SFTP for file sharing, SSH and RDP for remotely connecting to another machine, and much more…
Anyway…sorry for the long comment reply, but this is all to say that it depends.
It’s best practice policy to be careful what you do when on someone else’s network and you know others are on it too because you never know who is on and what kind of tools or technology they have access to. Best to use common sense by not visiting suspicious/sensitive websites/apps on your most used devices or instead using throwaway accounts and devices if doing so, ones that won’t come back to identify you and ones you wouldn’t mind losing if lost. Such as, be careful about incriminating yourself if discussing crimes you’re committing or logging into something like an online banking app or website or checking your crypto wallet on the net.